Leafing quality aluminum pigments are commerically manufactured in ball mills using particulate aluminum, mineral spirits as diluent or slurrying agent, and stearic acid as lubricant. The process is generally described by Junius D. Edwards and Robert I. Wray on pages 8-11 of their book, "Aluminum Paint and Powder" (Third Edition, 1955, Reinhold Publishing Corp., Library of Congress No. 55-6623). The production of high quality leafing aluminum pigments also requires the presence of oxygen in the mill environment. For example, W. D. Jones states on page 212 of his book, "Fundamental Principles of Powder Metallurgy" (Edward Arnold Publishers, Ltd., London, 1960), ". . . it has been established that powder produced in the absence of oxygen will not leaf." U.S. Pat. No. 3,002,891, issued May 28, 1935, to E. J. Hall, also teaches the importance for oxygen being present in the mill (page 2, Section D, first column, lines 27-38).
Current production ball mills, however, are generally large, slowly rotating cylinders and they do not provide efficient aeration of the mill slurry. As a result, commercially-produced leafing pigments are manufactured under various degrees of oxygen starvation, with a resultant decrease in product pigment quality when compared with pigments milled under conditions where the nascent, developing aluminum surfaces have free access to both stearic acid and oxygen.